A model for the spectrum of Sakurai's object (V4334 Sgr)

Theoretical spectral energy distributions for Sakurai's object at 300–1000 nm are derived. A model-atmosphere grid with Teff=5000–6250 K and logg=0.0–1.0 is computed for the chemical composition of Sakurai's object using opacity sampling including molecular and atomic absorption. Opacity due to absorption in 20 band systems of diatomic molecules is computed using the JOLA technique. The theoretical fluxes are compared with the observed energy distribution in a spectrum of Sakurai's object taken in April 1997. It is shown that (a) the theoretical energy distributions agree well qualitatively with the observed spectrum and depend strongly on the effective temperature; (b) C2 and CN molecular bands are dominant in the visible and near-infrared spectrum, while atomic absorption is important at UV and blue wavelengths; and (c) comparison of the observed and computed spectra yields an effective temperature for Sakurai's object in April 1997 Teff≈5250–5500 K. The dependence of the computed spectra at 300–1000 nm on the input parameters and adopted approximations is also discussed.